Method and apparatus for lapping dies



A Nov. 19, 1946.

D. D. SYMMES METHOD AND APPARATUS FOR LAPPING DIES Filed March 6, 1945 3Sheets-Sheet l Pls. 1- 115.2. Fung: :5-

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Nov. 19, 1946.

D. D. sYMMEs l METHOD AND APPARATUS FOR LAPP`ING DIES Filedmarch e, 19453 Sheets-Sheet 2 INVENTORI Nav. 19,` 1946.5 D. D. sYMMEs 2,4L304 IMETHOD AND APPARATUS FOR LAPPING DIES Filed March 6, 1945 3 Sheets-Sheet3V Q y NA L 4 s@ @u i ("3 Q .r i N im 1 @l i y f gli@ @I Patented Nov.19, 1946 METHOD AND APPARATUS FOR LAPPING DIES Daniel D. Symmes, l/VestHaven, Conn., assignor to The American Steel and Wire Company of NewJersey, a corporation of New Jersey Application March 6, 1945, SerialNo. 581,197

6 Claims.

The present invention relates to improvements in the method and meansfor lapping wire drawing dies or the like.

Among the objects of the invention are:

To obtain accurate control of the entrance and eXit angles of the dieperforation; Y

To obtain accurate control of the size of the diameter of theperforation;

To obtain precision control of the axial length of the bearing or throatportion of the die perforation;

To provide means for readily varying the axial length of the throat orbearing of the die perforation;

To obtain rounding in the region where the entrance and approachanglesof the die opening merge with the bearing throat portion thereof;

To obtain with great precision any predetermined entrance and exitrelief angles, diameter of the working throat portion, and length ofsaid bearing or throat portion;

To provide precision mechanism for automatically performing theoperations necessary to lap the perforation of a drawing die to acontour as viewed in longitudinal section, corresponding to twooppositely outwardly flaring straight-walled frusto-conical entrance andexit portions with a substantially cylindrical bearing portion ofpredetermined length between them.

It has been the common practice in the wire drawing industry for manyyears, to condition wire drawing dies by lapping the perforations of thedies. In the earlier days the die perforations were conditioned bymanually controlled lapping operations, and expert die makers acquiredgreat skill. Nevertheless, the human element entered into the operation,and the uniformity of die conditioning on a large scale was practicallyimpossible. In other words, with the manually controlled operations itis dicult to produce a great quantity of dies having identically thesame contour of perforation as viewed in longitudinal section. As theart progressed, different types of lapping or die conditioning machineswere proposed. These usually involved rotating the die and reciprocatingthe lap through the perforation therein while at the same time varyingthe angularity of the lap with respect to the axis of the perforation.So far as I am informed, all such prior mechanical means have resultedin forming a die perforation which, when viewed in longitudinal section,corresponded to a parabolic curve. Thus the throat or working region ofthe die was in a restricted zone or area, the wire being drawn makingcontact with a very short portion of the die.

Under my invention, as will hereinafter more fully appear, I propose todepart from the prior practice of relying upon the skill of the operatorto determine the contour of the die perforation, and I also depart fromthe later practice which heretofore has resulted in producing a diehaving a parabolic contour as viewed in longitudinal section through theperforation. As pointed out more fully hereinafter, under my invention Iso control the lapping operation that `thelapping tool or needle is heldor dwells at Va predetermined angle for a predetermined time intervalwith respect to the longitudinal axis `of the die perforation, and foranother time interval Iprovide for holding the lapping tool or needleand causing it to dwell in a position substantially coincident with thelongitudinal axis ofthe die-perforation. In this way I obtain a dieperforation contour which as viewed in longitudinal section correspondsto two oppositely flaring straight-walled frusto-conicalentrance andeXitvportions separated by a substantially cylindrical straight walledthroat or bearing portion, and I provide means for accurately holdingthe lapping needle or tool in the desired positions for predeterminedtime intervals and also provide means forl momentarily oscillating thelapping tool or needle for a short interval of time so as to round offthe angular corners in the transition regions between the ends of thethroat portion and the inner extremities of the outwardly aringfrustoconical entrance and relief portions.

For a more complete understanding of the invention, reference should bemade to the fol1owing detailed description, the accompanying drawings,and the appended claims.

In the drawings:

Figures 1, 2 and 3 illustrate different sequential steps in my improvedmethod of die conditioning.

Figure 4 is a greatly enlarged view through the perforation of a Wiredrawing die made by the improved method and apparatus herein claimed.

Figure 5 is an enlarged detail View of a portion of apparatus 'used incarrying out the invention.

Figure 6 is an enlarged view illustrative of the action of the lappingtool or needle at the completion of the lapping of the oppositelyflaring entrance and exit portions of the die perforation. l Figures 7,8 and 9 `are sections similar to Figures 1, 2 and 3 but omitting thelapping tool in the interest of clarity in the designation ofcharacteristics of different parts of the die perfora tion.

Figure is a front elevation of a machine involving novel features ofconstruction and arrangement designed for carrying out the hereinclaimed method. f I

Figure 11 is a plan view of Figure 10.

Figure 12 is an end elevation as viewed from the right end of Figure 10.

Figure 13 is a development of a control cam shown in Figures 10, 11 and12, effective to maintain the die lapping tool or needle inpredetermined positions.

Referring more particularly to the drawings, I have shown in Figure 4 agreatly enlarged view of a die having a perforation therein formedaccording to the herein claimed method and by the improved apparatus Ihave devised for carrying out the method. In this figure the die isshown with a 90 beveled portion I0 which may be molded, cast, or formedin any conventional manner since it forms no part of the invention. Theinvention has particular reference to the method and means for formingwith great precision the oppositely flaring straight-walled entrance andexit portions I2 and I4 and the substantially cylindricalstraight-walled throat or bearing portion I6 located intermediate suchentrance and exit portions. Y

As shown in Figure 4, the entrance and exit portions I2 and I4 formstraight-walled oppositely aring jfrusto-conical cavities separated bythe bearing portion I6 which is straight-Walled and substantiallycylindrical, although, as will hereinafter appear, the throat or bearingportion I6 may have a slight taper` corresponding to that of theparticular lapping tool or needle used.

' According to my improved method of die lapping, I start with a diehaving a roughly formed perforation therein of approximately the shapeshown in Figure 4. This may be a new die, or it may be one that has beenin use and requires refinishing. In carrying out the improved method Iemploy a lapping tool or needle such as indicated at I8, which has along slender working portion 20 tapered, for example, to a 1 includedangle. In starting the operation the lapping needle I8 is enteredthrough the die perforation at a predetermined angle, and is chargedwith a suitable abrasive mixed with kerosene oil, olive oil, or thelike. The lapping needle is clamped by chuck 22 to a spindle 24 carryinga collar 26 of such diameter that when inclined with its lower edge'resting on top of a, slide 28, the angle a between the axial centerline m-n of the lapping tool makes a predetermined angle with the axiso--p extending longitudinally through the center of the die perforation.The die spindle 24 passes through a guide opening 21 in the slide 28. Aweight 29 is secured to the lap so as to tend to move it downwardly.'I'he lapping operation is complete when the collar 26 is moveddownwardly by the weight 29 sufficiently to brin-g the lower face ofsaid collar flush with the upper face of the slide 28', with the lap inthe vertical position of Figure 2.

Reciprocating movements are imparted to the slide at predetermined timeintervals through a follower 36 by a control cam 30 having dwellportions 32-and 34, as shown by the development in Figure 13. The dwellportion 32 Serves to hold the lapping tool for a predetermined timeinterval in an angular position (for example, that of Figures 1 and 5)to suit the desired angle of the entrance and exit portions, and thedwell portion 34 serves to hold thelap for a predetermined time intervalin a position coinciding with the longitudinal axis of the dieperforation as indicated in Figure 2. The cam also has an undulatedportion including a rise 38 and a depression 4!! effective to quicklyshift the lap back and forth from the full line to the dottedline'position of Figure 3, so as to cause the lap to round oif thecorners I3 at the transition regions where the entrance and exitportions I2 and I4intersect the intermediate throat or bearing portionI6. These periodic dwells for the approach and relief angles and dwellfor the throat size and oscillations for rounding the bearing corners,are recurrent throughout the entire die conditioning cycle, and whilesuch operations are being periodically performed the cam 64 at theproper time imparts a vertical reciprocating motion to the slide 28which in turn lifts and lowers the lap, thus avoiding ringing orscratching of the wall `of the die perforation. Y

A tension spring 3| has one end secured to a rib depending from theVslide 28 and the other end secured to a xed anchorage, and thus tendsto hold the cam follower 36 against the active face of the cam 30. Thespindle 24 is conveniently formed of round tubing having a flattenedface portion 25, for coaction with the flat face 21' ofthe aperture 21,so as to normally prevent turning of the spindle 24.

The die to be conditioned is mounted on a platen 42 and secured theretoin any suitable manner. This platen is rotatably supported on anantifriction bearing 44 and is adapted to be driven at a high rate of.speed by a pulley 4B and a belt 48 trained around a pulley 50 carriedon a shaft 52 driven by a motor 54 through a suitable reduction -gearunit 56. The shaft 52 carries a worm 58 which meshes with and drives aworm wheel 60 secured to a shaft 62 mounted in suitable bearings asshown. This shaft carries a cam 64 which is adapted to rock a lever 66secured to a rock shaft 68 carrying arms 'I6 which in response tomovements of the cam 64 periodically lift and lower the slide 28, thelatterbeing mounted in guide members I2 movable vertically in ways 'I4formed at the upper extremity of xed standards 16. In the machineillustrated the slide 23 is horizontally disposed and is periodically orintermittently shifted in a horizontal direction, under control of thecam 3IJ, for certain predetermined distances to correspond with theparticular angle a to suit the desired taper of the entrance and exitportions of the die under treatment. 'Ihe cam 64 controls the Verticallowering and lift-` ing of the slide 28, and this cam is preferably sodesigned that no vertical movement will be imparted to the slide 28while the lapping tool dwells in the angular position of Figure 5.Preferably the vertical movement of the slide 28 is effected by the cam64 during the time interval that the axis of the lapping tool I8 and itsholder 24 is vertically positioned coincident with the axis o-p of thedie perforation.

Proper coordination of the action of the cams 64 and 30 is readilysecured, since the shaft which carries the cam 64 has secured near oneextremity thereof a worm 'I8 which meshes with the worm wheel which iskeyed or otherwise secured to the shaft 82 on which the control cam 3Uis mounted.

From the foregoing it is apparent that the ma'- chine shown anddescribed has been especially constructed and arranged for carrying outmy improved method of dielapping. In this method of lapping, a greatnumber of dies can be lapped simultaneously since the `single controlcam 38 will determine the angular disposition of a plurality of lappingneedles V2li -coacting with a plurality of dies carried by correspondingplatens 42. Each die is placed on a corresponding platen 42. A collar 26of a predetermined diameter is selected for the bearing length desired.This collar is slipped over the spindle 24 and is held thereon byasuitable set screw. As shown in Figure 5, the lower peripheral edge ofthe collar rests on the upper face of the slide 28. Since the collar isperpendicular to the axis m--n of the spindle and lapping tool I8, theunder face of the collar makes an angle with the upper face of the slide28 which is equal to the angle between the lines m-n and o-p. In the dieillustrated this anglais 8.5" in each case. Thus theincluded angle ofthe entrance portion of the die with the setting shown will be 17 plusthe 1 taper of the needle, or 18, and the exit portion will be 17 minus1 or 16, all as indicated by way of example in Figures 4, and 6. Asillustrated by way of example in Figure 5, the lower face of the collar26 makes an angle r with the upper face of the slide 28 which is equalto the angle a between the lines m-n and o p. The length of the side ofthe triangle opposite the angle :c is readily determined by`trigonometry from the formula b=r times tangent of 8.5

r being the radius of the `collar which corresponds to the adjacent sideof the angle With the lap I8 tapered to form a 1 included angle andextending for a uniform straight distance as at s inFigure 6, it is`possible to accurately calculate the diameter d, Figure 6, at the planein the die where the entrance and relief angles meet. The spindle axisin the example illustrated in Figures 5 and 6 being at an angle of 8.5",a right triangle y is formed as indicated in Figure 6, whose hypotenusecoincides with the plane where the entrance and exit angles intersect.The distance the lapping tool I 8 will finally enter the die is equal tothe distance marked b in Figure 6, which is the same as the distance bmarked in Figure 5. With these angles and lap tapers, the longitudinallength or extent of the bearing portion indicated by the dimension lineb2 in Figure 4 will always be the same regardless of the throatdiameter. If a longer or shorter bearing length b2 is desired, a similarchange in the collar radius r will accomplish the desired result.

Figures '7, 8, and 9 are longitudinal section representations of threefaces of die perforation as the same is conditioned at different stagesof my improved method.

Figure 7 illustrates the result of the first stage of the operation,after the lapping tool I8 has dwelt for a predetermined time interval;for example, at the 8.5 angle illustrated in Figure 1. In this ligure itis noted that the upper frustoconical entrance portion I2 is formed toan included angle one degree greater than the lower frusto-conical exitportion I4, due to the onedegree included angle between the opposedfaces of the lapping needle. Obviously if the lapping needle were trulycylindrical and not tapared, the entrance and exit angles would beequal.

Figure 8 illustrates the condition of the die after the lapping tool I8has dwelt for a predetermined time interval in a position in which itsaxis is coincident with the longitudinal axis of the die perforation,thus forming the substantially .cylindrical bearing 4or throat portionlias shown, which will have the slight taper corresponding to that ofthe tool I8, which is V2 on each side ofthe center line, as shown, forexample, in Figure 6.

Figure 9 illustrates the result of the oscillating action of the tool I8after it has acted to lround oif the corners at `the region where theapproach and exit angles I2 and I4 meet the substantially cylindricalbearing portion II of the die. The `detailed features of the foregoingImethod and apparatus as described andillustrated are to be interpretedin an illustrative rather than a limiting sense, since variousmodiiications may be made by those skilled 'in the art without departurefrom `the spiritandscope of the invention as defined in the appendedclaims.

I claim:

1. In a machine for lapping drawing dies, a support adapted to carry adie having a perforation to be lapped to a predetermined contour asviewed in longitudinal section, a lapping needle whose end is adapted toproject through the die perforation, means `:for effecting relativerotation between the support and the lapping needle, means for causingthe lapping needle to dwell for a determined time interval at apredetermined angle to the longitudinal axis of the perforation in thedie and then to `move to a position coincident with said axis and dwellin said coincident position for a determined time interval whereby theperforation in the die is contoured by the action of said needle toconform to two straightwalled outwardly iiaring frusto-conical entranceand exit portions separated by an intermediate straight-walledsubstantially cylindrical bearing portion.

2. In a machine for lapping drawing dies, a rotatable support adapted tosupport a perforated die whose perforation is to be lapped to apredetermined contour as viewed in longitudinal section, a lappingneedle whose end is adapted to project through the die perforation,means for causing the needle to dwell for a determined time interval ata predetermined angle to the longitudinal axis of the perforation in thedie and then to move to a position coincident with said axis and dwellin said coincident position for a determined time interval whereby theperforation in the die is contoured by the action of said needle toconform to two straight-walled outwardly flaring frusta-conical entranceand exit portions sep- 'arated by an intermediate straight-walledsubstantially cylindrical bearing portion.

3. In a machine for shaping wire drawing dies, a rotatable supportadapted to hold a drawing die having a perforation therein to be lappedto a predetermined contour as viewed in longitudinal section, a holdercarrying a lapping tool having an end portion projecting into the dieperforation, a slide with which the holder coacts, a collar secured tothe holder and adapted to coact with the slide and a cam for shiftingsaid slide having one dwell portion effective to hold the slide in aposition toV incline the tool at a predetermined angle t0 thelongitudinal axis of the die opening for a determined time intervai andhaving another dwell portion effective to maintain the slide in anotherposition to maintain the holder and the lapping tool carried thereby ina position for a determined time nterval wherein their common axiscoincides with the longitudinal axis of the die perforation, whereby thedie is contoured by the action of said tool to conform to twostraight-walled outportions separated by an intermediate straightwalledsubstantially cylindrical bearing portion.

4. In a machine for lapping wire drawing dies, a rotatable supportadapted to hold a die having a perforation therein to be lapped to apredetermined contour as viewed in longitudinal section, a holdercarrying a lapping tool having an end portion projecting into thedieperforation, a slide with which the holder coacts, a collar secured tothe holder and adapted to coaot with the slide, and a cam for shiftingsaid slide having one dwell portion effective to hold the slide in aposition to incline the tool at a predetermined angle to thelongitudinal axis of the die opening for a determined time interval andhaving another dwell portion effective to hold the slide in anotherposition to maintain the holder and the lapping vtool carried thereby ina position for a determined time interval wherein their common axiscoincides with the longitudinal axis of the die perforation, whereby thedie perforation is contoured by the action of -said tool to conform totwo straight-walled outwardly flaring frusto-conical entrance and exitportions separated by an intermediate` straight-walled subrstantiallycylindrical bearing portion, said cam also having an undulated portioneiective to oscillate the lapping tool so as to round oft' the wall ofthe die perforation at the region of the intersections of saidfrusto-conical entrance and 'exit portions with said intermediatebearing portion.

5. In the lapping of drawing dies, the method which comprises providinga die having a longitudinal perforation including connecting oppositelytapered entrance and exit portions, rotating the die about the axis ofthe perforation thereof while subjecting the wall of the perforation tothe action` of anelongated substantially cylindrical lapping toolextending through the perforation and contacting said tapered entranceand exit portions, causing said tool rst to dwell at a predeterminedangle to the longitudinal'axis of the die perforation for apredetermined time interval and later causing Vsaid'tool to dwell in aposition substantially coincident with said longitudinal axis of the diefora determinedtin'ie interval, whereby the perforation in the dieisaccurately contoured to conform to two straightwalled outwardly Haringfrusto-concal entrance and exitportions separated by an intermediatestraight-walled substantially cylindrical bearing portion. v. p Y

6. In the lapping of drawing dies, the method which comprises providinga die having a longitudinal vperforation including connecting oppositelytapered entrance and exit portions, rotating the die about the axis ofthe perforation thereof while subjecting the'wall of the perforation tothe action of an elongated slightly tapered lapping needle of round vcross section Yextending through the perforation and contacting saidtapered entrance and exit portions, causing said tool rst to dwell at apredetermined angle to the longitudinal axis of the'die perforation fora predetermined timev interval and-later causing said tool to dwell in aposition substantially cincident with said longitudinal axis of the diefor a determined time interval, whereby-the perforation in the die isaccurately Contoured` to conform to two straight-,walled outwardlykHaring frusto-conical entrance and exit portions separated by anintermediate straight-walled substantially cylindrical bearing portion.`L Y l DANIEL D. SYMMES. K

